System of frequency conversion



Aug. 18, 1942.

A. A. STUART, JR

SYSTEM OF FREQUENCY CONVERSION 2 Sheets-Sheet 1 Filed June 20, 1940 A. A. STUART, JR

SYSTEM OF FREQUENCY CONVERSION Aug. 18, 1942.

Filed June 20, 1940 2 Sheets-Sheet 2 Patented Aug. 18, 1942 SYSTEM OF FREQUENCY CONVERSION Alfred A. Stuart, In, Closter, N. J., assignor to Bendix Aviation Corporation, South Bend, Ind., a corporation of Delaware Application June 20, 1940, Serial No. 341,564

' 9 Claims. (01. 250-36) This invention relates to thermionic tubes and tube circuits, and more particularly to means for the conversion of alternating current frequencies from one value to another.

Many systems for the multiplication of frequencies, particularly radio frequencies, have been devised in the past, but the best of these systems are limited by their complexity, by the amount of power which can be handled in a single stage of frequency multiplication, or by low factors of frequency multiplication.

By means of the present invention, a simple system is provided by which frequencies may be multiplied without the objections existing in the prior art systems.

One of the objects of the present invention is the provision of a thermionic tube which, by novel construction and by a particular electrical and spatial relation of electrodes, will effect a predetermined frequency multiplication of a fundamental source.

Other objects include the provision of a new' system for the obtaining of variable frequencies and for the multiplication or division of frequencles, of an alternating current source in a system having high factors of multiplication or division.

These-and other objects of the present invention will become readily understood upon a study of the following specification when made in conjunction with the attached drawings, throughout which like parts are designated by like reference characters.

Fig. 1 is a perspective view of the thermionic tube of the present invention;

Fig. 2 is another perspective view of the new tube; and

Fig. 3 is a schematic diagram of a novel circuit embodying the tube of the present invention.

In accordance with the present invention, a source of oscillations of polyphase alternating current is used to dynamically bias grid elements in a new type of vacuum tube in such a manner as to create a rotating beam of electrons, which in rotation, will impinge upon segmental anodes and set up, in an output circuit, a frequency of a predetermined multiple value of the frequency of excitation and of single or polyphase character, as desired.

Having particular reference to Figs. 1 and 2, there is shown at 9.a thermionic tube having a sealed envelope ll] of glass, metal, or other suitable material, having a press member II for supporting the electrodes of the tube. These electrodes include a cathode member |2 which may ment lead l5 and anode leads 30 and 3|.

be an elongated cylinder of any suitable electron emitting material which is indirectly heated by a filament |3 having leads l4 and I5. Four grid members l6, ll, l8 and I9 are symmetrically arranged about cathode l2, and closely adjacent thereto. These grid members are supported at one end by a disk 20 of insulating material, such as glass, and by a, similar disk 2| at the other end. Disks 20 and 2| are maintained in spaced relation to each other and are rigidly supported within envelope ill by means of wires '22 and 23 which engage disks 20 and 2| in preformed peripheral grooves. I

symmetrically arranged about cathode I2, and relatively distantly spaced from cathode l2 and grids l6, ll, l8 and 9 are two series of anode members 24 and 25-which are supported upon hub connectors 26 and 21 by a plurality of wires 28 and 29, respectively. Hub members 26 and 21 are, in turn, held rigidly in space within envelope H) by means of wire leads 30 and 3| which also are brought out of the sealed press II to form connections to a direct .current source (not shown) of anode voltage. Radio frequency choke coils 30' and 3| are formed in leads 3!! and 3|, respectively, close to hub connectors 26 and 21. Further support to the series of anodes 24 and 25 is given by means of vertical supporting wires 32 and 33 which are bent horizontally at their upper ends and sealed into a glass rod member 34. Output connections in the form of rod members 35 and 36, are connected at their inner ends to hub members 26 and 21, and at their outer ends 31 and 38, respectively, are sealed to envelope I0. Arm-like members 39 and 40 extend outside the sealed portion of tube 9. Flexible connectors 4|, 42, 43 and 44 are attached at their inner ends to grid members l6, I1, l8 and I9, respectively, and are sealed at their outer ends to projections 45, 46, 41 and 48 upon the surface of envelope Ill. The terminal connector members, such as extension rods 39 and 4|], and leads 5|, 52, 53 and 54 of grid connectors 45, 46, 41 and 48 are provided for connection of the tube to an external circuit which will be described later. A lead 55 for external connection of cathode I2 is brought out of press member along with fila- Each of wires 22 and 23 are joined together at their ends as indicated at 56 and 51 and are supported by upright wire members 58 and 59 which extend into press member Wire member 58 carries current from lead l4 of filament |3 through the wire spreader 60 which acts as a spacing member for disks 20 and 2|.

A novel frequency multiplying circuit employing the tube just described, is shown in Fig. 3, wherein 8| is a sourceof alternating current, the frequency of which is to be multiplied, having its output connected to the primaries 82 and 83 of transformers 84 and 85, respectively. Shunted across alternator 8| is an adjustable resistor 88 and a variable condenser 81 joined together by center-tap 88, which is also connected to one end of each of transformers 84 and 85. With resistor 88 and condenser 81 adjusted to have particular values, the voltage in primary 82 will be 90 degrees out of phase with the voltage in primary '83. As this is a common form of phase splitting system, it will be readily understood without further explanation. Secondary 68 of transformer 84 has its center portion connected to a biasing battery I0, while secondary 1| of transformer 85 likewise has its center portion connected to a biasing battery 12. Leads I8 and I4 are connect ed to grid members I8 and I8, while leads I5 and I6 are connected to grid members I1 and I8, respectively. Anode or segmental plate members 24 are joined together through conductor 11 and to output lead I8, while anode members 25 are connected together through conductor 19, which is connected to output lead 88. Leads 18 and 88 are connected to opposite ends of primary 8| of transformer 82 which is tuned by means of a variable condenser 83 in shunt therewith, to the frequency to which it is desired to multiply the frequency of source 6|. Primary 8| has a center tap 84, by means of which suitable anode potential from a source, such as battery 85, may be connected to anodes 24 and 25. The secondary 88 of transformer 82 is connected to any suitable load, such as, for example, an antenna, a resistance or another amplifier, or another frequency multiplier.

By connecting the split phases of source 8|, as shown, a rotating electrical field is set up in the tube, as the polyphase voltages are impressed upon grids I6, II, I8 and I9. Grids I8 and I! are electrically out of phase with grids l8 and I9 by 90 degrees, and by suitable biasing imposed through batteries III and I2, the electrons emitted from cathode I2 are restricted to a narrow beam or sheet, such as indicated by 81. This beam or sheet, extending between cathode l2 and anodes 24 and 25, is rotated at a speed depending on the frequency of source 8| through the medium of the rotating electrical field caused by phase splitting.

By virtue of the connection of battery 85 to anodes 24 and 25, a high potential exists in the anode and cathode circuit in the absence of a beam of electrons 81. As the beam impinges upon any one of the segmental plates 24 or 25, such as that one of plates 25 shown in Fig. 3, current flows from battery 85 to the particular segmental plate 25 upon which beam 81 impinges, and to the cathode through ground, back to the battery 85. When current flows, a magnetic field is, of course, set up in the primary of transformer 8|, which induces an alternating current in secondary coil 88. In one complete cycle of alternation of source 6|, beam 81 will have swept through a complete circle and will have impinged upon each of the segmental plates that make up anodes 24 and 25. Therefore, if N=the number of segmental plates in tube III, N impulses will have been set up in primary 8| and will have induced an alternating current, N/2 times in secondary 88. The output frequency source 6 I therefore, determined by the speed of rotation (cycles per second) of beam 81 and the number of pairs of plates that make up anodes 24 and 25.

It will be seen, therefore, that a frequency appears across terminals of secondary 88, the stability of which is a measure of the stability of Since cathode I2 is made of appreciable extent, beam 8'! exists throughout the length of cathode I2 and thus, the current that flows through the anode-cathode circuit can be of appreciable value, giving a frequency, not only in a fixed multiple, either odd or even, of an exciting source, but which is also of substantial power.

Since a real multiplied frequency appears in the output of the tube, the tuned circuit made up of coil 8| and condenser 83 is not essential I to the obtaining of the multiplied frequency, and

it is provided merely to aflorda circuit of low impedance and good wave form to the multiplied frequency.

If the out-of-phase relation between the currents in transformers and 85 is varied from 90 degrees, then a varying frequency appears in the output of the tube. The actual variation in frequency per degree of displacement of the 90 de gree phase relation can be demonstrated matheniatically, but for present purposes it suffices that variation of the 90 degree relationship varies the speed of the beam 81 for different portions of a complete cycle of rotation, and the output frequency apparent in leads l8 and 88 will vary through a predetermined number of cycles per second.

The circuit shown in Fig. 3 can be used for the obtaining of either audio or radio frequencies.

f It is particularly well adapted to the obtaining upon large anode voltage changes, which may result from certain types of loads that may be connected to the output of the circuit shown. Further, space charge grids may be placed in the space between cathode I2 and grid elements I8 to IS, in order to minimize the efiect of a space charge in this region and, if desired, suppressor grids in the region of anodes 24 and 25 may be electrically connected to cathode, or near cathode, potential in order to eliminate undesired charge conditions in the neighborhood of anodes 24 and 25.

Source of alternating current 8| is shown as being a single-phase alternator, with its output split into two phases, 90 degrees apart. It will be readily understood that a polyphase alternator may be substituted for the split-phase arrangement shown, and the circuit will be equally operative. Two-phase or split-phase excitation is shown principally because it seems to be the simplest to describe, but it is obvious that a different number of grids connected to three or more phases of excitation will result in a similar beam 81 sweeping anodes 24 and 25 at constant speed. Also, slight phase variations will cause the beam to move at a non-uniform rate, resulting in the obtaining of frequency modulation or available across the terminals of secondary 86 is,

a varying frequency in the output of the tube,

as has been described above. Also, for simplicity, the output of the multiplied frequency has been shown as single-phase, but it is obvious that a polyphase output may be obtained, if desired. Secondary-of transformer 85 may be connected to any source of utilization of the multiplied frequency, such as an amplifier of audio or radio frequencies, or another stage of frequency multiplication similar to that shown in Fig. 3. By means of the system of the present invention, frequencies may be multiplied at appreciable power levels due to the formation of beam 81 along the entire length of cathode I2.

While only one embodiment of the present invention has been shown, it is to be understood that the invention is not limited to this example, but by the scope of the appended claims.

What is claimed is:

1. A frequency multiplying circuit including a source of polyphase current, the frequency of which is to be'multiplied, an electronic tube having a cathode capable of emitting electrons, a plurality of anode members, a plurality of grid members interposed between said cathode and anodes, adjacent grids being equally spaced from one another and occupying separate angular positions, said grids being so connected to said source of polyphase current as to produce a revolving electrostatic field and restrict the electrons emitted into a narrow beam, a source of high potential, alternate anodes being connected together and to said source of high potential to form an output circuit, whereby, upon said beam rotating in sequence upon said anodes, an alternating current of the frequency desired may be set up in said output circuit.

A circuit for multiplying the frequency of an alternating current including an electronic tube having a cathode, a plurality of angularly spaced grids symmetrically disposed about said cathode and a plurality of anodes circularly spaced about said cathode, alternate anodes being connected together and to a source of anode potential, an input circuit including a source of polyphase current of the frequency to be multiplied, said source being connected in polyphase relation to said grids, so as to set up a rotating electric field in said tube, an electron emissive surface on said cathode, and an output circuit connected to said anodes and to said source of anode potential, whereby an alternating current of the desired multiple frequency will be set up in said output circuit through the rotation of electrons from said cathode by said electric field.

3. In a system of frequency multiplication, a source of alternating current, an electronic tube having a cathode, angularly spaced grids and anodes, said grids being symmetrically disposed about said cathode and connected to said source of alternating current in polyphase relation so as to set up a rotating field, alternate ones of said anodes being connected together and to opposite sides'of an output circuit containing a source of anode potential, whereby electrons emitted by said cathode will be rotated in a beam by said rotating field, impinging on each of said anodes in series, and setting up in said output circuit an alternating current of the frequency to which said source of alternating current is multiplied.

4. In a frequency conversion system, an input including a source of alternating current of fixed frequency, means for splitting the phase of said source by 90 degrees, an electron tube having an electron emitting cathode, a plurality-of grids, and a plurality of anodes, an output circuit connected to said anodes, said grids being connected in pairs out of phase electrically by degrees to therebyset up a rotating field carrying electrons about said cathode at a constant angular rate and set up a constant frequency in said output circuit, and means for varying the 90 degree phase split whereby a variable frequency, of valuedepending on the variation in phase split. will be set up in said output circuit.

5. In a system of frequency multiplication, a source of alternating current having polyphase leads, an electronic tube including a cathode, a plurality of angularly spaced grids and a plurality of anodes, said grids being symmetrically disposed about said cathode and connected in polyphase relation to said polyphase leads to set up a rotating field, a source of anode potential connected to said anodes, an output circuit including said source of anode potential, and means for biasing said grids to restrict electronic flow between cathode and anodes into a beam which revolves with said rotating field and creates the desired multiplied frequency in said output circuit.

6. A circuit for obtaining a variable frequency from a relatively fixed frequency source which comprises a source of alternating current of the relatively fixed frequency, a thermionic device including an electron emitting cathode, grids and a plurality of anodes equally spaced from said cathode, means including a source of anode potential for instituting flow of electrons from said cathode to said anodes, polyphase connections between said fixed frequency source and said grids for setting up a rotating field, biasing means associated with said grids to restrict said electrons to a beam rotating in synchronism with said rotating field, means for varying the polyphase relations of said polyphase connections, and an output circuit connected to said anodes for receiving a frequency which varies with phase variation of said polyphase connections.

7. A circuit for the multiplication of frequencies which includes a source of alternating current to be multiplied, an electronic tube having an electron-emissive cathode, a plurality of grids angularly and symmetrically spaced about said cathode, a plurality of pairs of anodes equi-distantly spaced fromsaid cathode and beyond said grids, the anodes of each of said pair being electrically connected together and leads from each pair being connected to an output circuit, said grids betherein, said cathode electrode extending alongan axis of symmetry, said grid electrodes being closely adjacent said cathode electrode, electrically insulated from said cathode and from each other and symmetrically disposed about said cathode electrode, said-anode electrodes being segmental plates equidistantly spaced from said cathode electrode and spaced angularly from each other and symmetrically disposed cylindrically about said cathode electrode, two connections for said anodes, means connecting adjacent anode plates to diflerent ones of said connections,

an output connection for each of said connections and terminals for the external connection of said cathode grids and anodes in a circuit.

9. A thermionic tube having a sealed envelope, a cathode, grids and anodes therein, said cathode being linear along a central axis, said' grids being angularly spaced and electrically insulated from each other, equidistantly spaced from said 

